Consider a spiral galaxy that is moving directly away from Earth with a speed V = 3.240 105 m/s at its center, as shown

Consider a spiral galaxy that is moving directly away from Earth with a speed V = 3.240 × 105 m/s at its center, as shown in FIGURE 25-40.

In figure 25-40

The galaxy is also rotating about its center, such that points in its spiral arms are moving with a speed v = 5.750 × 105 m/s relative to the center. If light with a frequency of 7.308 × 1014 Hz is emitted in both arms of the galaxy, what frequency is detected by astronomers observing the arm that is moving
(a) Toward and
(b) Away from Earth? (Measurements of this type are used to map out the speed of various regions in distant, rotating galaxies.)

Earth